1. Field of the Invention
The present invention relates to a semiconductor package preferably applied to electronic apparatuses such as a personal computer, an electronic circuit device, and a mounting method of a semiconductor device.
2. Description of the Related Art
In recent years, in electronic apparatuses in which a plurality of semiconductor devices are mounted therein, such as a personal computer and a wireless communication apparatus, in order to meet a demand for miniaturization, electronic components to be built in have been miniaturized, the number of pins have been increased, and a semiconductor package has increasingly tended to be thinned among the electronic components. In the semiconductor package, a warp preventive countermeasure, for example, by reflow soldering at the time of solder mounting is required, and various countermeasures have been proposed (see Jpn. Pat. Appln. KOKAI Publication No. 11-163186, for example).
To realize further thinning of the semiconductor package, structural changes for thinning all constituting elements as objects are required such as reduction of a chip thickness or a mold resin thickness, and stopping of a solder ball.
Under an influence of the structural change, the semiconductor package is further easily warped or twisted at the time of the solder mounting. Therefore, with only the existing countermeasure, the soldering is not achieved, solder shortage is generated in the vicinity of a corner pad, or further the package is sometimes warped or twisted. Accordingly, there is a problem that heights of the mounted components are misaligned or increase. Especially when a large number of remarkably thinned semiconductor packages are mounted on predetermined circuit substrates such as a mother board, dimensional accuracy of the board after mounting the package is influenced by the warps of the semiconductor packages, or misaligned mounting height by occurrence of the twisting.
As described above, there has been a demand for further highly reliable mounting technique with the thinning of the semiconductor package in the mounting technique of the semiconductor package.